Microphones are widely applied in daily life devices configured to convert the received voice into the electrical signals, such as cell phones, voice recorder, telephone, interphone, and headset. Comparing to conventional microphones, the microphones manufactured by a semiconductor process have many behaviors of miniaturization, energy-saving and multifunction, etc. Moreover, a miniature microphone and an analog amplification circuit packaged to form single MEMS microphone product are prevalent in current market.
There are three common types of MEMS microphone including piezoelectric MEMS microphones, piezoresistive MEMS microphones, and capacitive MEMS microphones, wherein the piezoelectric MEMS microphone and the piezoresistive MEMS microphone are lower in sensitivity to sound pressure and have larger system noises. So now the capacitive MEMS microphones having higher sensitivity and lower power consumption characteristics are becoming the more predominant mainstream MEMS microphone development in current market.
Please refer to FIG. 1. The capacitive MEMS microphone 100 includes a substrate 101, a membrane 110, a backplate 120 having porous structure, and an insulating air layer 130 disposed between the membrane 110 and the backplate 120. The membrane 110 and the backplate 120 are configured to serve as a conductive plate. The capacitive MEMS microphone 100 is configured to convert sound into voltage, and the conversion principle is described as follows: the membrane 110 is vibrated by the sound pressure, wherein the vibration of the membrane 110 will bring a dynamic micro-displacement between the membrane 110 and the backplate 120 to change a capacitance value of the capacitive MEMS microphone 100, and the changed capacitance value will be converted into voltage. Moreover, the insulating air layer 130 arranged between the membrane 110 and the backplate 120 is configured to prevent charges from accumulating in the capacitive MEMS microphone 100.
However, it is difficult for conventional process for manufacturing MEMS microphones to completely remove a sacrificial layer originally located at the same position of the insulating air layer 130 and form the clearly defined (and properly formed) insulating air layer 130. But if the residues of the sacrificial layer are remained between the membrane 110 and the backplate 120, then the residues will result in a reduced reliability of the capacitive MEMS microphone and result in higher power consumption.
In view of the aforementioned reasons, there is need to provide a new method for manufacturing MEMS microphones to solve the above mentioned problems resulted from the residues of the sacrificial layer.